It has been known in gasoline engines to use a heating device to prevent the freezing of the water content in air of the air/fuel mixture in a carburetor or the like (a phenomenon called icing) caused by the ambient temperature of the air or the evaporation heat of the gasoline, etc. When icing develops in the engine of a vehicle, there develops a condition which is tantamount to sudden braking which can result in an accident and thus, is a serious problem. Therefore, to prevent icing is an important consideration in engine design.
FIG. 16 shows a typical heating system for an internal combustion engine according to the prior art. Such a heating system uses a nichrome wire and/or the heated water from the cooling system of the engine for warming the carburetor. Typically, either a nichrome heater 50 or a warm water circulation type heater 51 is installed in the carburetor. For the sake of facilitating the explanation, a carburetor 40 with both of them being provided therein is shown.
First, a heating system for an internal combustion engine using a nichrome heater 50 will be described below. A nichrome heater is positioned adjacent that part of the fuel entry system which is cooled most such as an evaporator for the gasoline engine or throttle valve (not shown) of the carburetor 40. With the start-up of the engine, electrical current being supplied from the battery flows to the nichrome heater 50, with the result that the heater 50 warms the throttle valve and area around it thereby preventing possible icing of the carburetor.
Secondly, the heating system for an internal combustion engine, based on a warm water circulation type heater 51, will be explained below. With the start-up of the engine, water for the cooling of the engine is circulated through carburetor 40 as is indicated by the arrow in FIG. 16. As the temperature of the engine heats up, the temperature of the water for cooling also rises and then the carburetor 40 is warmed and icing is prevented by this cooling water. In some engines, oil is used for cooling purposes. In such a case, oil for cooling is employed in the place of water for cooling as described above.
FIG. 17 shows the use of a timer of the prior art for control of the electric current flowing through the nichrome heater 50. As shown in this figure, a timer circuit 60 comprises a crystal oscillator 61, a reference oscillation circuit 62 and a counting circuit 63. This timer circuit measures the time from start-up of the engine and controls a relay 65.
More specifically, crystal oscillator 61 is an element which oscillates at its intrinsic frequency. The reference oscillation circuit 62 is an oscillation circuit that generates an electric pulse which is in conformity with the intrinsic frequency of the crystal oscillator 61. The counting circuit 63 counts the pulses generated by the reference oscillator circuit 62 and then drives relay 65 at the time when a predetermined number of pulses has been reached. The relay 65 has a coil 66 and contact means 67 positioned between nichrome heater 50 and the electric power source. It is the relay circuit with relay 65 that controls operation of the nichrome heater. That is, the coil 66 is connected to timer circuit 60 and causes the opening and closing of contact means 67 in response to the output of the counting circuit 63.
Accordingly, after the start-up of the engine the reference oscillation circuit 62 generates a pulse of a frequency which is intrinsic to the crystal oscillator 61. This pulse is imputed into and counted by counting circuit 63. Upon the passage of a period of time after engine start-up, the pulse becomes constant, counting circuit 63 cuts off the electric current that flows to coil 66, thus contact means 67 opens and the electric circuit that flows to the nichrome heater is shut off.
If the coolant for the engine is used for heating, a temperature sensitive sensor such as a bimetal element can be provided to ultimately control the flow of such coolant.
The above described heating systems have had their problems.
In the case where a nichrome wire is used as a heating device, there is a need to cover the wire with an insulating material to provide electrical insulation from the body that contains the wire and the wire itself. This electrical insulation; however, greatly effects the transmission of the heat to the carburetor/body, thus limiting the efficiency of the system.
This inefficiency of the heating system becomes particularly troublesome in the case of a motor cycle where the electric generating capacity is small. In these cases, it has been difficult to generate sufficient heat. Additionally, because of the use of the insulating material, the size of the nichrome heater needs to be larger. At the same time, the diameter of the nichrome wire needs to be kept at a minimum to raise the resistance and heating value with the result that the wire lacks durability.
In the case of using engine coolant as a heat source, there is the problem of the initial start-up time period when the coolant is still not heated and, thus, the icing problem cannot sufficiently be prevented.
Still further, the timing system for the nichrome heater suffers from reliability problems due to the stringent environments in which it is employed in either an automobile engine area or a motorcycle engine.
Lastly, in the case where the electric current capacity of the nichrome heater is larger, the contact means must be large to carry the current; and correspondingly, the electric current that flows to the coil also is larger, thereby providing for large current consumption. Such a system is generally also large in size.